Human fibroblasts, in culture, undergo a period of rapid proliferation which is followed by a decline in the rate of proliferation and the eventual demise of the culture. It has been suggested that this phenomenon is genetically intrinsic to the cell, and may represent aging at the cellular level. Cultured fibroblasts exhibit a layer of stainable material adherant and external to the cell membrane. This cell coat consists of glyco-proteins, glycolipids, and polysaccharide components termed glycosaminoglycans. The quantity and type of glycosaminoglycain has been noticed to vary in cells following viral transformation and hormonal treatment. In addition, the amount and composition of glycosaminoglycans in connective tissue has been noted to change during development and during normal aging. The glysaminoglycan content of connective tissue matrix is presumed to play a role in producing and maintaining the properties of hydration, charge, and permeability which are characteristic of that tissue. The role of glycosaminoglycans at the cell surface is not defined. Whether the glycosaminoglycan synthesis and organization of cultured fibroblasts changes with serial subcultivation or donor age and whether there are differences in surface composition and organization which may affect these cells and the matrix to which they contribute, is the subject of this proposal. Specific objectives include: (1) determination of the differences in quantity and composition between glycosaminoglycans produced by early and late-passage human embryo fibroblasts and between cells from young and old donors; (2) characterization of the synthetic route of these molecules in each culture group; (3) an investigation of the nature of the association between glycosaminoglycans and the cell membrane; and (4) the isolation and characterization of proteoglycan monomers and aggregates produced by cultured fibroblasts.